The drain plug for crankcases of most internal combustion engines used today is essentially the same as the drain plugs used in the first internal combustion engines as documented in my U.S. Pat. Nos. 4,231,544, Nov. 4, 1980; and 4,298,182, Nov. 3, 1981.
It has been estimated that 60% of the motoring public or 85 million American motorists in 1980 changed their own oil and it is believed that this estimate has risen in the last two years. Even though the price of gasoline has decreased recently, the price of motor oil has not and motorists continue to seek ways to reduce the high cost of driving. Changing the oil in an automobile remains a dirty job, the plug can be mislaid, and if not properly threaded back into the crankcase opening, the threads can become stripped and an oversize plug required.
Inventors in this field have been active, but as yet, the standard plug is used on all new production cars sold in the United States and the use of after market drain plug alternatives remains miniscule.
The first efforts to replace the standard drain plug took the form of mechanisms to enable the oil to be drained by simply operating a remote mechanism on the dash board. Such devices may be seen in such U.S. patents as U.S. Pat. No. 2,095,696, Oct. 12, 1937; No. 2,657,705, Nov. 3, 1953; No. 3,049,334, Aug. 14, 1962; No. 3,677,369, July 18, 1972; No. 3,954,250 May 4, 1976; and No. 4,086,981, May 2, 1978. In addition to the extra cost of these mechanisms, it is still necessary to get under the car to catch the used oil so little is gained by the expenditure. More importantly, however, it is essential that the mechanism be fail-safe since loss of engine oil can result in severe damage to the engine. The use of a complicated mechanism only increases the possibility of failure of the mechanism and loss of engine oil.
Since the collection and disposal of used oil is a problem to the weekend mechanic U.S. Pat. No. 3,874,478, Mar. 20, 1974, provides a valve and collection bag.
The valve member and spring retainer, however, must be detached from the mechanism and both may be mislaid.
Another valve and used oil collection device is taught in U.S. Pat. No. 4,025,048. This device has no positive means for locking the device in the closed position and could inadvertently become unscrewed and leak.
My own U.S. Pat. Nos. 4,231,544 and 4,298,182 supra solved the locking problem but market acceptance has been slow due to the preference for metal crankcase drain valves instead of the use of plastic taught in my patents. Further, the proliferation of foreign and U.S. small four (4) cylinder cars has resulted in the use of many different crankcase hole sizes and different threads so that the necessity of providing many different sizes is not cost effective for plastics.
This application discloses a crankcase drain valve which uses a slide gate with a positive locking spring.
Examples of slide valves without locking springs are taught in U.S. Pat. No. 303,656, Aug. 19, 1884; U.S. Pat. No. 450,588, Apr. 14, 1891 and United Kingdom Pat. No. 17,246, 1894. The United Kingdom patent discloses a rubber band closure device which is not considered to be a locking spring.